Physics > Optics

Title:
An electromagnetic black hole made of metamaterials

Abstract: Traditionally, a black hole is a region of space with huge gravitational
field, which absorbs everything hitting it. In history, the black hole was
first discussed by Laplace under the Newton mechanics, whose event horizon
radius is the same as the Schwarzschild's solution of the Einstein's vacuum
field equations. If all those objects having such an event horizon radius but
different gravitational fields are called as black holes, then one can simulate
certain properties of the black holes using electromagnetic fields and
metamaterials due to the similar propagation behaviours of electromagnetic
waves in curved space and in inhomogeneous metamaterials. In a recent
theoretical work by Narimanov and Kildishev, an optical black hole has been
proposed based on metamaterials, in which the theoretical analysis and
numerical simulations showed that all electromagnetic waves hitting it are
trapped and absorbed. Here we report the first experimental demonstration of
such an electromagnetic black hole in the microwave frequencies. The proposed
black hole is composed of non-resonant and resonant metamaterial structures,
which can trap and absorb electromagnetic waves coming from all directions
spirally inwards without any reflections due to the local control of
electromagnetic fields and the event horizon corresponding to the device
boundary. It is shown that the absorption rate can reach 99% in the microwave
frequencies. We expect that the electromagnetic black hole could be used as the
thermal emitting source and to harvest the solar light.